In logistic or manufacturing fields, in order to hold an object and move it to a desired place, a driving apparatus installed on a tip of a manipulator or the like is employed. The driving apparatus is preferably lightweight, wire-saving, compact, and capable of outputting high power.
For this purpose, as an actuator used in a joint or the like of the driving apparatus, a hydraulic actuator energized by fluid is usually employed rather than an electromagnetic actuator.
As the hydraulic actuator, a McKibben type actuator used as an artificial muscle of a robot is known in the art. The McKibben type actuator is structured by a tubular expandable member and a sheath which covers the expandable member. The McKibben type actuator obtains a necessary actuating force by contracting the expandable member in its longitudinal direction and expanding the expandable member in its radial direction. However, since the expandable member of the McKibben type actuator repeats contraction and expansion, the expandable member may be damaged by rubbing with the sheath. In addition, since the expandable member of the McKibben type actuator is contracted in its longitudinal direction and is expanded in its radial direction, there are a lot of moving parts. Therefore, it is difficult to predict a deformation transition of the expandable member and to mechanically strongly fix it to the driving apparatus under considering its deformation transition in advance. For this reason, in order to produce a driving apparatus capable of holding an object to fit a shape of the object, a structure of the driving apparatus becomes complicated.